Selective isomerization of 1-olefins to 2-olefins

ABSTRACT

A process for the selective isomerization of 1-olefins to 2olefins comprising the contacting of a 1-olefin with a sodium coated, calcium metal aluminosilicate molecular sieve catalyst at temperatures of about the freezing point of the 1-olefin being isomerized to about 150* C.

[ 51 Oct. 10,1972

iMcDonough et al.

1 SELECTIVE ISOMERIZATION OF 1- OLEFINS TO Z-OLEFINS [72] Inventors:John M. McDonough, 8004 South Menard, Oak Lawn, Ill. 60459; Linsley S.Gray, Jr., 3948 Forest Avenue, Downers Grove, 11]. 60515 [22 Filed:March 1, 1971 21 Appl.No.: 119,917

' 52 US. Cl ..260/683.2, 252/455 51 Int. Cl ..C07c 5/24 [58] Field ofSearch ..260/683.2

[56] References Cited UNITED STATES PATENTS 2,988,578 6/1961 Fleck etal...260/683.2

3,013,986 12/ l 961 Castor ..252/455 3,150,202 9/ 1964 Holt et al..260/683.2 3,236,909 2/1966 Winnick ..260/683.2

Primary Examiner-Delbert E. Gantz Assistant ExaminerC. E. SpresserAttorney-Francis W. Young, Walter H. Steinbauer, Jr. and Alexander &Speckman [57] ABSTRACT A process for the selective isomerization ofl-olefins to 2-olefins comprising the contacting of a l-olefin with asodium coated, calcium metal aluminosilicate molecular sieve catalyst attemperatures of about the freezing point of the l-olefin beingisomerized to about 150 C.

12 Claims, No Drawings SELECTIVE ISOMERIZATION OF l-OLEFINS TO Z-OLEFINSBACKGROUND OF THE INVENTION and require the use of prohibitivelyexpensive and often hazardous reagents. In attempts to avoid the manydisadvantages connected with the direct production of 2- olefins,processes have been designed to achieve such products from theisomerization of l-olefins. Unfortunately, such processes havepreviously resulted in undesirable skeletal isomerization,dehydrogenation, disproportionation, polymerization and/or short lifeisomerizing catalyst activity.

It is a primary object of this invention to provide a process forproducing 2-o1efins.

It is a more particular object of this invention to produce 2-olefinsfr'om l-olefins by a selective isomerization process.

It is another object of this invention to provide the isomerization oflong hydrocarbon chain l-olefins to 2- olefins at conversion levels ofat least 70 percent.

It is yet another object of this invention to provide high conversion ofl-olefins to 2-olefins without substantial skeletal isomerization,dehydrogenation, disproportionation and/or polymerization.

Additionally, it is an object of the present invention to accomplishselective l-olefin to 2-olefin isomerization through the utilization ofa catalytic system which provides relatively long catalyst life.

Other objects and advantages of the invention will become apparent uponreading the following description and specific examples.

In accordance with the present invention a l-olefin is effectivelyisomerized to a 2-olefin by contacting the 1- olefin with a calciummetal aluminosilicate molecular sieve which is coated with a monoatomiclayer of sodium metal. This process is extremely desirable in terms ofspecificity and speed, since relatively high conversions of l-olefinichydrocarbons to 2-olefinic hydrocarbons of 70 percent or better areachieved at room temperature in relatively short periods of time. Also,side effects such as other skeletal isomerization, dehydrogenation,disproportionation and/or polymerization typically characteristic ofother isomerization processes are minimized by the process of thisinvention. Furthermore, the catalytic system employed has been found tohave a relatively long, useful life.

The selective isomerization process of this invention involves only thethree terminal carbon atoms of the lolefins. Suitable olefins for use inthis invention are structurally represented as follows:

wherein the total number of carbon atoms is from about six to about 25,and preferably about six to about 18; R, is selected from the groupconsisting of straight chain alkyls containing one to three carbon atomsand hydrogen, although preferably R is hydrogen; and R is a substituentwhich does not react with sodium, and may include straight or branchedchain alkyls containing three to 22 carbon atoms and preferably aboutthree to 15 carbon atoms. The R group may contain functional radicalswhich do not react with sodium.

Typical l-olefinic materials which may be used include l-hexene,l-heptene, l-octene, l-nonene, ldecene, l-hendecen'e, l-dodecene,l-tridecene, ltetradecene, l-pentadecene, l-hexadecene, l-heptadecene,l-octadecene, l-nonadecene, l-eicosene, lheneicosene, l-docosene,l-tricosene, l-tetracosene, l-pentacosene, 3-methyll -peritene,4-methyll -pentene, 3-methyl-l-hexene, 4-methyl-l-hexene,. "5- methyl- 1-hexene, 3-methyll -heptene, 4-methyll -heptene, 6-methyl-l-heptene,3-methyl-l-octene, 4- methyl- 1 -octene, S-methyll -octene, 7-methyl- 1-octene, 3-ethyl-l-pentene, 3-propyl-l-hexene, 4-ethyl-1- hexene,3-ethyl-l-heptene, 4-ethyll-heptene, S-ethyll-heptene,4-propyl-1-octene, 5-propyl-l-octene, 6- ethyll -octene, 6-propyll-nonene, 7-propyll -decene, 8-ethyl-1 -hendecene, S-ethyll -dodecene,6-propyl-'1- tridecene, l l-ethyll -tetradecene, l2-propyll-pentadecene, 9 -ethyll -hexadecene, IO-propyl- 1 eicosene, 7-ethyll-heneicosene, l 9-propyll docosene and l6-ethyl-l-tricosene. Mixtures ofolefinic hydrocarbons are suitable as feed stocks for the process of thepresent invention.

The catalytic material of the present invention is important to theexcellent results achieved. A calcium metal aluminosilicate molecularsieve coated with a monoatomic layer of sodium metal must be employed toachieve the objects of this invention. The basic calcium metalaluminosilicate molecular sieve is commercially available (Union CarbideCorporation, Linde Division) and is typically produced by percent ionexchange of calcium ions for sodium ions of the sodium metalaluminosilicate sieves which may be represented by the general formula:

The calcium metal aluminosilicates have internal surface areas ofgreater than 500 and typically about 650 to 800 square meters per gramand external areas of about 1 to 3 square meters per gram. The averagevolume of their voids is about 0.38 cubic centimeters per gram. Suchsieves may be obtained in either pellet or powdered form.

In order to transform the calcium metal aluminosilicate sieve to thecatalyst utilized in the process of this invention, it is necessary tocoat its surface, by adsorption thereon, with a monoatomic layer ofsodium metal. Disposition of the monoatomic sodium metal layer may beperformed in any suitable manner. An extremely convenient methodinvolves intimately contacting an activated calcium metalaluminosilicate sieve with a vapor of sodium metal in an inertatmosphere as taught by U.S. Pat. No. 3,013,986, the disclosures ofwhich are incorporated herein by reference.

The catalyst of this invention may be first prepared by activating acalcium metal aluminosilicate molecu- I In any case, a monoatomic layerof the sodium metal is adsorbed by the molecular sieve.

In each of the above alternative procedures, the quantity of sodiummetal which is necessary to coat the calcium metal aluminosilicate sieveas a monoatomic layer will vary with the surface area of the sieve.Therefore, exact weight percents of sodium necessary to coat the sieveas a monoatomic layer cannot be given generallyJnstead, the quantity ofsodium metal necessary to coat a given calcium metal aluminosilicatesieve must be determined, individually, for each case. Normally about 12to about 16 percent by weight of sodium metal, based on the weight ofthe calcium metal aluminosilicate sieve, is required for coating when apowdered sieve is used. If the sieve is not adequately coated with anessentially monoatomic layer of sodium metal a loss of catalyticactivity causing a corresponding decrease in the specificity ofconversion of l-olefins to 2-olefins will result. Also, if excessiveamounts of sodium metal are used for coating, desired catalytic activitywill again decrease.

The resulting sodium coated, calcium metal aluminosilicate catalystisuniquely selective in isomerizing l-olefinic hydrocarbons to2-olefinic hydrocarbons as a result of its unusual property of initiallyfavoring formation of 2-olefins. However, this preference is timelimitedand will give way to formation of other internal olefins such as3-olefin, 4olefin, etc., after a given period of time. Suitableresidence times are dependent on the type of l-olefin being isomerizedand the reaction temperature. Therefore, care must be taken to isomerizel-olefins only within that time interval during which other internalolefin production is kept to a When the hydrocarbon solvents areincluded within the contacting system environment, the reactiontemperature may be lowered to about the freezing point of the solventfor the isomerization of l-olefins which remain soluble in thehydrocarbon solvent at such temperatures. Such hydrocarbon solventspreferably have freezing points of about down to 80 C. Suitable minimum.Such minimum production is less than about and preferably less thanabout 5 percent.

Utilizing the process of this invention, l-olefinic to 2- .olefinicconversions in excess of 70 percent can be achievedin relatively shortperiods of time, such as 10-15 minutes at ambient temperature of about25 to about 35 C, and atmospheric pressure. Typically, such conversions,as in the case of l-hexadecene to 2-hexadecene, approach 90 percent.While room temperatures can normally be utilized, reaction temperaturesmay vary from about the freezing point of the l-olefin being isomerizedto about 150 C. The reaction temperature at which isomerization takesplace will also vary with the residence time at which the isomerizationreaction is to be conducted.

The reaction temperature can be lowered if a hydrocarbon solvent orsolvents is included within the contacting system environment providedthe l-olefin being isomerized is soluble in the hydrocarbon solvent andthe sodium coating does not react with the solvent.

hydrocarbon solvents which may be used are pentane, hexane and heptane.Consequently, the reaction temperatures in such a system may be about Cto about C. For purposes of process convenience, however, with orwithout use of hydrocarbon solvents, preferred reaction temperatures arefrom about 20 C to about 40 C.

The residence time during which a 2-olefin is produced from theisomerization of a specific l-olefm while maintaining production ofother internal isomers to conversion levels of less than about 10percent, can.

be readily determined. This is done by continuously takingrepresentative samples at noted time intervals during the isomerizationreaction and analyzing the collected samples to determine double bonddistribution by such methods as gas chromatography, or nuclear magneticresonance spectroscopy. By noting the analyses the residence timerequired to achieve the conversion levels set forth above, i.e., lessthan 10 percent conversion of l-olefin to internal olefins other than2-olefin, can be determined. Explicit residence times cannot be givensince such will vary with the isomerization reaction system beingemployed. After the isomerization reaction has been conducted for thedesired residence time, it is terminated by quenching by the addition ofa material such as petroleum ether to the reaction system and separatingthe liquid and solid phases. The produced olefins are then collected andseparated into their 1 and 2 isomers by such techniques as fractionaldistillation. After this separation, the lolefin may be recycled forcontinued use in the selective isomerization process of this inventionand the 2- olefin is collected as a final product.

The olefinic hydrocarbon is contacted with the sodium coated calciummetal aluminosilicate sieve catalyst in either a batch or continuoussystem. When a batch system is employed as the processing mode thelolefinic hydrocarbon is intimately mixed with the sodium coated calciumaluminosilicate sieve in a fixed volume such as a reaction vessel. Whenperformed via a continuous processing system, the l-olefinic hydrocarbonis passed through a column containing a sodium coated calciumaluminosilicate catalyst bed. However, regardless of the reaction systemused, care must be exercised that substances which are reactive withsodium metal are not included as part of the system environmentsubsequent to the disposition of the sodium metal onto the calcium metalaluminosilicate sieve.

The, following Examples are given to illustrate preferred embodiments ofthis invention.

EXAMPLE I Preparation of Sodium Coated Calcium Metal AluminosilicateSieve Catalyst 40 grams of a free-flowing powder of calcium metalaluminosilicate sieve (available from Union Carbide Corp. Linde Divisionas X Molecular Sieve) were placed in a three-neck round-bottom flaskequipped with a mechanical stirrer, nitrogen inlet and outlet and atemperature sensing port. The free-flowing sieve powder was blanketedwith a dry nitrogen flow and heated with stirring to 200 C. 6 grams ofsodium metal were added in Agm chunks. Upon melting, the sodium metalformed a uniform coating over the sieve powder forming a dark gray toblack powder as a result of vigorous continued stirring. The resultingproduct was a sodium monoatomic coated calcium metal aluminosilicatesieve. This catalyst was allowed to cool, stirring being discontinuedwhen temperature below the melting point of the sodium metal wasachieved.

EXAMPLE n Isomerization of l-Hexadecene 42.5 grams of a calcium metalaluminosilicate sieve (available from Union Carbide Corp., LindeDivision as 10X molecular sieve), coated with 6.5 grams of sodium inaccordance with the procedure given in Example I, were produced in aflask and the flask then maintained at a temperature of 25 C.Subsequently, 101 grams of l-hexadecene were added to the flask. Thecontents were mixed continuously. A sample, withdrawn after 10 minutes,was analyzed via gas chromotagraphy. The analysis showed that thel-hexadecene was isomerized to 88 percent 2-hexadecene and 8 percent3-hexadecene. Four percent remained as l-hexadecene.

EXAMPLE Ill lsomerization of 4-methyl-l-hexene 43.0 grams of a calciummetal aluminosilicate sieve (available from Union Carbide Corp., LindeDivision as 10X molecular sieve) coated with 6.1 grams of sodium inaccordance with the procedure given in Example 1, were produced in aflask and the flask then maintained at a temperature of 25 C.Subsequently, 12.3 grams of 4-methyl-l-hexene were added to the flaskalong with 81.8 grams of l-hexadecene solvent. The contents were mixedcontinuously. A sample withdrawn after minutes, was analyzed by nuclearmagnetic resonance after separation of the 4methylhexenes from thehexadecene by distillation. The analysis showed that the4-methyl-l-hexene was isomerized to 70 percent 4-methyl-2-hexene andonly trace amounts of 4-methyl-3-hexene.

The following are given as illustrative experiments, the results ofwhich illustrate, by comparison, the unexpected results of the presentinvention in selectively isomerizing l-olefins to 2-olefins.

ILLUSTRATIVE EXPERIMENT I Attempted lsomerization of l-I-lexadecene WithA Non-Sodium Coated Calcium Metal Aluminosilicate Sieve 42.5 grams of acalcium metal aluminosilicate sieve (available from Union Carbide Corp.,Linde Division as 10X molecular sieve) were added to a flask maintainedat a temperature of 23 C. Subsequently, 101.4 grams of l-hexadecene wereadded to the flask. The

contents were mixed continuously. A sample withdrawn after 50 minutes,was analyzed via gas chromatography. The analysis showed the sample tobe percent l-hexadecene.

ILLUSTRATlVE EXPERIMENT ll Attempted lsomerization of l-Hexadecene WithA Sodium Coated Sodium Metal Aluminosilicate Sieve 37.5 grams of asodium metal aluminosilicate sieve (available from Union Carbide Corp.,Linde Division as 13X molecular sieve), coated with 5.1 grams of sodiurnin accordance with the procedure given in Example I, were added to aflask maintained at a temperature of 25 C. Subsequently, 95.0 grams ofl-hexadecene were added to the flask. The contents were mixedcontinuously. Samples withdrawn after 30 and 90 minutes were analyzedand found to contain no 2-hexadecene.

While in the foregoing specification this invention has been describedin relation to certain preferred embodiments thereof, and many detailshave beenset forth for purpose of illustration, it will be apparent tothose skilled in the art that the invention is susceptible to additionalembodiments and that certain of the details described herein can bevaried considerably without departing from the basic principles of theinvention.

We claim:

1. A process for selectively isomerizing a l-olefin to a 2-olefinwithout substantial skeletal isomerization, dehydrogenation,disproportionation and polymerization comprising contacting saidl-olefln at a temperature of about the freezing point of the l-olefinbeing isomerized to about C with a calcium metal aluminosilicate sievecoated with a monoatomic layer of sodium metal for a time sufficient toeffect conversion of the l-olefin to the 2-olefin.

2. The process of claim 1 wherein the olefinic hydrocarbon isrepresented by the following formula:

wherein the total number of carbon atoms is about six to about 25; R, isselected from the group consisting of straight chain alkyls containingone to three carbon atoms and hydrogen; and R is any substituent whichdoes not react with sodium.

3. The process of claim 2 wherein the reaction temperature is about 20 Cto about 40 C.

4. The process of claim 2 wherein the reaction temperature is 25-3 5+ Cand the reaction is maintained at that temperature for a residence timeof 10 15 minutes whereby the l-olefin is isomerized to 2-olefin atconversion levels of at least about 70 percent.

5. The process of claim 4 wherein the number of carbon atoms is aboutsix to about 18.

6. The process of claim 4 wherein the l-olefinic hydrocarbon is selectedfrom the group consisting of lhexadecene and 4-methyll -hexene.

7. The process of claim 2 wherein the calcium metal aluminosilicatesieve is in powdered form and is coated said solvent being non-reactivewith sodium and in which the l-olefin is soluble.

11. The process of claim 10 wherein the hydrocarbon solvent has afreezing point of about down to C 12. The process of claim 11 whereinthe l-olefin, the hydrocarbon solvent and the calcium aluminosilicatesieve are contacted at a temperature of about 80 C to about C.

k' l I

2. The process of claim 1 wherein the olefinic hydrocArbon isrepresented by the following formula: wherein the total number of carbonatoms is about six to about 25; R1 is selected from the group consistingof straight chain alkyls containing one to three carbon atoms andhydrogen; and R is any substituent which does not react with sodium. 3.The process of claim 2 wherein the reaction temperature is about 20* Cto about 40* C.
 4. The process of claim 2 wherein the reactiontemperature is 25*-35+ C and the reaction is maintained at thattemperature for a residence time of 10 - 15 minutes whereby the 1-olefinis isomerized to 2-olefin at conversion levels of at least about 70percent.
 5. The process of claim 4 wherein the number of carbon atoms isabout six to about
 18. 6. The process of claim 4 wherein the 1-olefinichydrocarbon is selected from the group consisting of 1-hexadecene and4-methyl-1-hexene.
 7. The process of claim 2 wherein the calcium metalaluminosilicate sieve is in powdered form and is coated with about 12 toabout 16 percent by weight of sodium metal as based on the weight of thecalcium metal aluminosilicate sieve.
 8. The process of claim 2 whereinR1 is hydrogen.
 9. The process of claim 2 wherein R is selected from thegroup consisting of straight chain and branched chain alkyls containingthree to 22 carbon atoms.
 10. The process of claim 2 wherein saidcontacting of the 1-olefin and the calcium metal aluminosilicate sievecoated with a monoatomic layer of sodium metal is conducted in thepresence of a hydrocarbon solvent, said solvent being non-reactive withsodium and in which the 1-olefin is soluble.
 11. The process of claim 10wherein the hydrocarbon solvent has a freezing point of about down to-80* C.
 12. The process of claim 11 wherein the 1-olefin, thehydrocarbon solvent and the calcium aluminosilicate sieve are contactedat a temperature of about -80* C to about 150* C.